Inner seal for the piston of a rotary piston machine

ABSTRACT

This invention relates to an annular seal for the face of the piston of a rotary piston machine of the trochoidal type, of which the housing comprises two end portions and a peripheral wall portion with a multi-lobed inner surface, in which the piston is mounted to rotate on an eccentric, the seal having at least two scraper rings which are urged resiliently against the adjacent end wall of the housing to prevent the passage of coolant or lubricant into the working chambers. Such seals are known as inner seals.

O United States Patent 1 1 3,843,283 Wilmers Oct; 22, 1974 [54] INNER SEAL FOR THE PISTON OF A 3,171,590 2/1965 Bentele et al 418/142 3,309,01 3/1967 Osakada et al. 418/142 ROTARY PISTON MACHINE 3,396,708 8/1968 Tado 418/ 142 Inventor! Gottlieb Wilmers, Neuenstadt, 3,400,939 9/1968 Jones 4l8/l42 Germany 3,415,444 l2/l968 Frenzel 418/142 1 Assignees: Audi NSU Aum Union 3,506,275 4/l970 Morlyama 4l8/l42 Aktiengesellschaft, Neckarsulm/Wurttemberg; Wankel Primary Exammer c Husar GmbH, LindaulBodensee both of, Attorney, Agent, or Firm-Kane, Dalslmer, Kane, Germany Sullivan and Kurucz [22] Filed: Mar. 20, 1973 [57] ABSTRACT [2]] Appl. No.: 343,151

This invention relates to an annular seal for the face of the piston of a rotary piston machine of the trochoidal [30] Foreign Application Priority Data type, of which the housing comprises two end portions Mar. 24, 1972 Germany 7211239 and a peripheral wall portion with a multi-lobed inner surface, in which the piston is mounted to rotate on an [52] US. Cl. .Q 418/142 e oentric, the seal having at least two scraper rings [51] Int. Cl. F01c 19/12 which are urged resiliently against the adjacent end [58] Field of Search 418/142 wall of the housing to prevent the passage of coolant or lubricant into the working chambers. Such seals are [56] References Cited known as inner seals.

UNITED STATES PATENTS 7 Claims, 3 Drawing Figures 3,139,233 6/l964 Slmonsen 4l8/l42 l it l gi it 0.

INNER SEAL FOR THE PISTON OF A ROTARY PISTON MACHINE BACKGROUND OF THE INVENTION In a known inner seal for the piston of a rotary piston engine of the trochoidal type two scraper rings are arranged to be fixed in a carrier which is urged by an elastic O-ring towards the end wall of the housing, so that the scraping edges of the scraper rings press against the 1 end wall. In this arrangement it is not possible for both scraper rings to engage continuously against the end wall of the housing. Moreover the O-ring is subjected to severe heating by the piston and its life is consequently short.

SUMMARY OF THE INVENTION The object of the invention is to provide an inner seal which achieves effective engagement of both scraper rings against the adjacent end wall of the housing and in which the elastic O-ring, if indeed required at all, is arranged so that it is subjected to the heat of the piston only to a slight degree.

This and other objects are achieved according to the invention in that the scraper rings are arranged between the axial limb and the radial limb of a backing ring of L-shaped cross section, the radially inner scraper ring being located in a radial direction by the inner peripheral surface of the radial limb of the backing ring and the radially outer scraper ring being located on the inner scraper ring, and there being a gap between the outer scraper ring and the backing ring, and a resiliently yielding sealing ring being arranged between the two scraper rings and the radially inner scraper ring being non-detachably and tightly connected to the backing ring by an annular disphragm.

Such an inner seal can be produced as a complete unit ready for installation and is pressed into a circular opening in the end wall of the piston. The gap between the outer scraper ring and the axial limb of the backing ring prevents the possibility of this scraper ring jamming. The provision of the yielding sealing ring be tween the two scraper rings ensures a relatively long path for the flow of heat from the hot piston to this sealing ring, thereby reducing the thermal loading to which the latter is subjected, so that even if it is an O-ring of elastomeric material it has an adequate working life. The diaphragm which connects the inner scraper ring to the backing ring prevents the passage of the working medium through the gap between the inner scraper ring and the backing ring into the interior of the piston and despite this allows practically frictionless movement of the scraper rings. This diaphragm can be constructed so that it exerts an axial spring force on the inner scraper ring so that no separate engaging spring is needed for this scraper ring.

Instead of an O-ring one could also employ a metallic ring of C-shaped cross section, exerting a spring force in a radial direction.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional view of the invention take through an inner seal and the adjacent components of the piston and its housing;

FIG. 2 is an end elevation view thereof; and

FIG. 3 is a sectional view of a modification of the invention taken through an inner seal and the adjacent components of the piston and its housing.

DETAILED DESCRIPTION In the drawing an end wall of a piston is indicated at l, and its face 2 defines, together with the end wall 3 of the adjacent end portion 4 of a housing, a gap 5. To seal this gap an annular so-called inner seal indicated 0 generally at 7 is pressed into the circular opening 6 in the end wall I of the piston. This inner seal comprises a backing ring 8 of L-shaped cross-section, having an axial limb 9 and a radial limb 10 extending radially inwards from the axial limb. The backing ring 8 receives two scraper rings 11 and 12, arranged concentrically one within the other, urged by wavy springs 13 and 14 against the end wall 3 of the housing. The wavy springs abut against the radial limb 10 of the backing ring 8. The radially inner scraper ring 11 is provided with an axial extension 15 by which it is centered, i.e., located in a radial direction, on the inner peripheral surface 16 of the limb 10 of the backing ring 8. The outer scraper ring 12 is located on the inner scraper ring 11, and be tween the limb 9 and the outer scraper ring 12 there is a gap 22 which prevents jamming of the outer scraper ring 11 when the backing ring 8 is pressed into the opening 6. Between the two scraper rings 11 and 12 there is an O-ring 18 of elastomeric material which seals the gap between the two scraper rings and prevents the passage of coolant or lubricant from the space 19 radially inside the inner seal 7 via the space 20 between the scraper rings 11 and 12 and the backing ring 8 into the gap 5 between the face 2 of the piston and the end wall 3 of the housing. In the reverse direction the working medium can penetrate through the gap 5 and the annular gap 22 between the axial limb 9 of the backing ring 8 and the outer scraper ring 12 into the space 20 and assist the engagement of the scraper rings 11 and 12. In order to prevent the passage of the working medium through the gap 17 between the inner scraper ring 11 and the radial limb 10 of the backing ring 8 into the cavity of the piston the inner scraper ring 11 is tightly and permanently connected to the backing ring 8 by an elastic annular diaphragm 21. The diaphragm 21, which has a U-shaped cross section, is connected by its limbs to the backing ring 8 and to the scraper ring 11, for example by a press fit, by adhesive or by soldering or brazing.

The inner scraper ring 11 is centered on the backing ring 8 by abutment of its leg 15 on the surface 16 of the backing ring 8. Naturally this abutment is never gas tight nor oil tight because the scraper ring must move axially relative to the backing ring 8. Therefore, the resilient annular diaphragm 21 is provided which bridges gap 17. i

As shown in FIG. 2, the seal of the present invention is designed for use with a conventional type rotary piston engine. The general components of the engine would include piston 30, mounted on the eccentric 31 of an eccentric shaft 32. A housing 33 surrounds piston 30 and has a multi-lobed inner surface 34 so as to provide the necessary working chambers for operation of the engine.

In a modification of the embodiment illustrated by way of example, the annular diaphragm 21 can be made so stiff that it exerts an axial force on the inner scraper ring 11 and urges that ring against the end wall of the housing, so that the wavy sping 13 can be omitted. Alternatively in place of the two wavy springs 13 and 14 an appropriately shaped single spring can be provided for causing engagement of both scraper rings 11 and 12.

In place of the elastic O-ring 18 we could use a metallic ring of C-shaped cross section (FIG. 3), acting resiliently in a radial direction, and it has the advantage of greater resistance to heat.

Thus the several aforenoted objects and advantages are most effectively attained. Although a single somewhat preferred embodiment of the invention has been disclosed and described in detail here, it should be understood that this invention is in no sense limited thereby and its scope is to be determined by that of the appended claims.

What is claimed is:

1. An inner annular seal for the piston of a rotary piston machine of the trochoidal type, of which the housing comprises two end wall portions and a peripheral wall portion with a multi-lobed inner surface, in which the piston is arranged to rotate on an eccentric, the inner seal comprising at least two scraper rings, means for resiliently urging the rings against the adjacent end wall of the housing, a backing ring of L-shaped cross section and having a radial limb with an inner peripheral surface and an axial limb, the scraper rings being arranged between the axial limb and the radial limb of the backing ring of L-shaped cross section, the inner scraper ring being located by the inner peripheral surface of the radial limb of the backing ring and the outer scraper ring being located on the inner scraper ring.

2. An inner seal according to claim 1, in which a radial gap is provided between the outer scraper ring and the backing ring.

3. An inner seal according to claim 1 in which a resiliently yielding sealing ring is arranged between the two scraper rings.

4. An inner seal according to claim 3 in which the sealing ring between the two scraper rings is formed as an O-ring of elastomeric material.

5. An inner seal according to claim 3 in which the sealing ring between the two scraper rings is formed as a metallic ring of C-shaped cross section acting resiliently in a radial direction.

6. An inner seal accordin to claim 1 in which the inner scraper ring is permanently and sealingly connected to the backing ring by an annular diaphragm,

7. An inner seal according to claim 6, in which the annular diaphragm is formed so that it serves as an engaging spring for the inner scraper ring to urge it in use against the adjacent end wall of the housing. 

1. An inner annular seal for the piston of a rotary piston machine of the trochoidal type, of which the housing comprises two end wall portions and a peripheral wall portion with a multilobed inner surface, in which the piston is arranged to rotate on an eccentric, the inner seal comprising at least two scraper rings, means for resiliently urging the rings against the adjacent end wall of the housing, a backing ring of L-shaped cross section and having a radial limb with an inner peripheral surface and an axial limb, the scraper rings being arranged between the axial limb and the radial limb of the backing ring of L-shaped cross section, the inner scraper ring being located by the inner peripheral surface of the radial limb of the backing ring and the outer scraper ring being located on the inner scraper ring.
 2. An inner seal according to claim 1, in which a radial gap is provided between the outer scraper ring and the backing ring.
 3. An inner seal according to claim 1 in which a resiliently yielding sealing ring is arranged between the two scraper rings.
 4. An inner seal according to claim 3 in which the sealing ring between the two scraper rings is formed as an O-ring of elastomeric material.
 5. An inner seal according to claim 3 in which the sealing ring between the two scraper rings is formed as a metallic ring of C-shaped cross section acting resiliently in a radial direction.
 6. An inner seal accordin to claim 1 in which the inner scraper ring is permanently and sealingly connected to the backing ring by an annular diaphragm.
 7. An inner seal according to claim 6, in which the annular diaphragm is formed so that it serves as an engaging spring for the inner scraper ring to urge it in use against the adjacent end wall of the housing. 